Updated project metadata. The Atlantic salmon (Salmo salar) genome contains 10 chitinase encoding genes, but little is known about the function of these chitinases. Three of the chitinase genes have previously been shown to be expressed in the stomach tissue of Atlantic salmon. In the current study we show that the protein products of these genes, the family 18 glycoside hydrolase (GH18) chitinases, Chia.3, Chia.4 and Chia.7 are secreted into the stomach mucosa and are amongst the most abundant proteins in this matrix.